Honda Acty HA3/HA4 Fluids: What to Change. Service Manual Deep Dive
If your Acty arrived without service records, change the fluids and start a maintenance log. First, read the chassis code on the truck. This guide covers the 660cc E07A-era HA3 2WD and HA4 4WD trucks. It does not cover the earlier 550cc HA1/HA2 or the later HA6/HA7.
This is a baseline guide, not a substitute for the chassis-specific service manual. Transmission type and trim still matter.
The short version
An HA3/HA4 baseline service should address:
Engine oil and filter
Manual transmission oil, if equipped
Front differential oil on HA4 4WD trucks
Coolant
Brake fluid
Automatic transmission fluid on automatic HA3 trucks, using the transmission-specific specification
Washer fluid
The rear final drive is part of the transaxle. Do not look for a separate rear differential housing simply because the truck is rear-wheel drive.
Verified specifications
The table below reports what the accessible English HA3/HA4 service manual actually states. It is not a universal shopping list.
System | Application | Manual-backed specification | Service quantity |
Engine oil | E07A | API SF 10W-30; the maintenance section also shows 5W-30 for -30°C to 0°C (-22°F to 32°F) | See capacity note below |
Manual transmission | HA3 2WD, 4MT/5MT | Honda MTF or API SE 10W-30 | 1.2 L at change |
Manual transmission | HA4 4WD, 5MT | Honda MTF or API SE 10W-30 | 1.2 L at change |
Manual transmission | HA4 4WD, 4MT UL/UR | Honda MTF or API SE 10W-30 | 1.4 L at change |
Front differential | HA4 4WD only | API GL-4; the service-data table does not state a viscosity | 0.46 L at change |
Coolant | Truck, manual transmission | Coolant type is not identified in the capacity table | 6.5 L total |
Coolant | Truck, automatic transmission | Coolant type is not identified in the capacity table | 7.1 L total |
These values come from the HA3/HA4 English service manual, service-data and maintenance pages.
Why the engine-oil capacity is not one neat number
The translated manual conflicts with itself. Its service-data table lists 2.5 L for an oil-only change and 2.7 L with a filter. The maintenance page lists 2.7 L oil-only and 3.0 L with a filter. Both cannot be the definitive refill amount.
RMMT's practical answer is to treat the published capacity as an estimate. Add less than the upper figure, check the dipstick on level ground, run the engine, let it settle, and check again. The dipstick decides the final level.
The same manual gives a normal engine-oil interval of 10,000 km (6,250 miles) or six months, with shorter service in extreme cold. For an older imported work truck, RMMT may recommend a shorter interval based on use, fuel dilution, leaks, and the condition of the oil. That is shop guidance, not the factory interval.
The Acty fluid mistake to avoid
Do not fill every drivetrain opening from the same bottle.
The HA3/HA4 manual calls for Honda MTF or the period-specified engine oil in the manual transmission, while the HA4 front differential is listed separately as API GL-4. The manual page does not support calling the front differential a generic GL-5 application, and it does not support publishing 75W-85 as a factory-stated viscosity.
If a bottle says only GL-5, do not assume it is a substitute. A product can be marketed as yellow-metal-safe and still have different synchronizer friction behavior from the fluid Honda specified. Use Honda MTF where the manual calls for it, or confirm a substitute against the exact application.
A clean baseline service
Start with the truck level and identify every fill point before opening a drain.
Confirm the chassis code and transmission type.
Loosen each fill plug before removing its drain plug.
Drain one component at a time so the fluids and plugs do not get mixed up.
Replace damaged sealing washers and inspect magnetic plugs for debris.
Refill to the manual's level procedure, then check for leaks.
Record the fluid brand, product name, specification, quantity, date, and odometer reading.
A thin gray paste on a magnetic plug can be normal. Chips, flakes, or needle-like pieces deserve investigation before the truck goes back to work.
Coolant deserves extra care
The Acty's engine and radiator are separated by long coolant runs. A quick drain-and-fill can leave air trapped in the system. Fill slowly, use the manual's bleed procedure, run the heater, and recheck the reservoir after the first complete heat cycle. Never remove the pressure cap while the engine is hot.
What is baseline advice, not a verified HA3/HA4 spec
RMMT recommends inspecting and replacing brake fluid when the truck's history is unknown. Because the available source does not tie one DOT rating to every HA3/HA4 configuration, confirm the truck's documentation or reservoir marking first. The same rule applies to automatic transmission fluid: identify the transmission before selecting ATF.
Before you order fluids
Send RMMT the chassis code, transmission type, and 2WD/4WD configuration. We can build a fluid list for the truck in front of you instead of guessing from a model name.
Sources and verification notes
Honda Acty HA3/HA4 English service manual — service data on PDF pages 32-40; oil and coolant maintenance on PDF pages 48-49. The manual is an English translation and contains the engine-oil capacity conflict described above.
KeiWiki Acty transmission-fluid reference — useful secondary cross-check. It lists GL-4 75W-85 for the HA4 front differential, but the service-data table checked for this draft confirms only API GL-4 and the change quantity. The article therefore does not present the viscosity as factory-verified.
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